This invention relates to flow control valve particularly suited for controlling the flow of solid particulate material through a conduit and sealing that conduit. The valve is of a type referred to as a clamshell valve.
The valve of the present invention is particularly designed for controlling the flow of dusty particulate material and is suitable for attachment to the bottom of a hopper for dust. One specific application of the invention is for use in a cement clinker cooler at the outlet of the hopper in the undergrate compartment.
In grate type cement clinker coolers, a bed of hot material discharged from a rotary kiln is supported on a grate system consisting of rows of alternating fixed and movable grate plates, each having a plurality of holes therethrough. Air under pressure is supplied to a plenum chamber below the grates for passage upwardly through the holes in the grate and the bed of material to cool the hot material. Fine particles of cement clinker may fall through the grates into the lower plenum chamber. Typically, there are hoppers at the bottom of the lower plenum chamber to collect the dust. Periodically, these hoppers must be emptied.
Prior to the present invention, it was common practice to utilize either slide gates or double tipping valves at the outlet of these hoppers which valve are capable of not only controlling the flow of material through the outlet of the hopper or conduits associated therewith, but also must seal against the air pressure in the plenum chamber during cooler operation.
Prior to the present invention, clamshell valves were known including a valve plate in the form of an arc with the outer surface of the arc being exposed to the dust or particulate material. Prior to the present invention, however, such valves would tend to leak after a period of operation because the valve element or plate would not seal due to the accumulations of material and misalignment. Also with prior valves, the mechanism for rotating the valve included an operating shaft which is located in the material flowpath. This can be a particular problem with abrasive materials such as cement clinker because the operating shaft will tend to be worn by the continuous exposure to the abrasive material.